FORM 2
THE PATENTS ACT 1970
(Act 39 of 1970)
&
THE PATENTS RULE 2003
(SECTION 10 and rule 13)
COMPLETE SPECIFICATION
"PROCESS FOR PREPARATION OF CRYSTALLINE ETORICOXIB"
Glenmark Pharmaceuticals Limited;
Glenmark Generics Limited
an Indian Company, registered under the Indian Company's Act 1957 and having its registered
office at
Glenmark House,
HDO - Corporate Bldg, Wing -A,
B.D. Sawant Marg, Chakala, Andheri (East), Mumbai - 400 099
The following specification particularly describes the invention and the manner in which it is to be performed.

PRIORITY
This application claims the benefit to Indian Provisional Application No. 2480/MUM/2012, filed on August 27, 2012 the contents of which are incorporated by reference herein. FIELD OF THE INVENTION
The present invention relates to a process for the preparation of crystalline etoricoxib. BACKGROUND OF THE INVENTION:
Selective inhibitors of cyclooxygenase-2 are a sub-class of drugs known as non-steroidal anti-inflammatory drugs (NSAIDs). Conventional NSAIDs block both forms of the cyclooxygenase (COX) enzyme and although active in reducing pain and swelling associated with the inflammatory process, can produce severe side effects. The identification of the COX-2 enzyme associated with inflammation has provided a viable target of inhibition which more effectively reduces inflammation and produces fewer and less drastic side effects. The selective COX-2 inhibitors (coxibs) were originally developed to minimize the adverse effects of conventional non-steroidal anti-inflammatory drugs (NSAIDs) while maintaining the same analgesic and anti-inflammatory properties.
Etoricoxib is known to exist in various polymorphic forms for example form I, form II, form III, form IV, form V, amorphous form and hydrated form.
Etoricoxib is a coxib, which is a class of arthritis/analgesia medications. Etoricoxib has been approved in Europe and is sold under the brand name Arcoxia®. Etoricoxib is chemically designated as 5-chloro-3-[4-methylsulfonyl)phenyl]-2-(2-methyl-5-pyridinyl) pyridine with the structural formula:


United States Patent No 6858631 (US'631) discloses polymorphic form I of etoricoxib characterized by powder X-ray diffraction (PXRD) pattern peak at 9.7 degrees 2 theta. US'631 further discloses form II of etoricoxib characterized by differential scanning calorimetry having an extrapolated onset of melting at 131± 1°C and a peak melting point of 132.5± 1°C.
United States Patent No 6441002 (US'002) discloses polymorphic form III, form IV, hemihydrate form and amorphous form of etoricoxib. Polymorphic form III was characterized by powder X-ray diffraction (PXRD) peak at 10.5, 16.1 or 22.4 degrees 2 theta. Polymorphic form IV was characterized by powder X-ray diffraction (PXRD) peak at 8.7 and 15.2. US'002 teaches hemihydrate form containing about 0.5 water per mol of etoricoxib.
European Patent No. 1296951B1 discloses form V of etoricoxib characterized by powder X-ray diffraction (PXRD) peak position at 13.7 angstroms.
It has been observed that crystalline etoricoxib characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, prepared according to known methods, on storage, gets converted to hemihydrate form, form IV, form V or mixtures thereof and is thus unstable.
The present invention provides a process for the preparation of a stable crystalline etoricoxib with peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, having no or little tendency to convert to any of the other polymorphic forms. The crystalline etoricoxib prepared according to the process of the present invention, remains stable on storage.
SUMMARY OF THE INVENTION
The present invention provides a process for the preparation of crystalline etoricoxib, characterized by powder X-ray diffraction (PXRD) pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta comprising:
a) treating etoricoxib with a solvent system comprising at least one solvent selected from the group consisting of glycols, polyalkylene glycols and mixtures thereof; and
b) isolating crystalline etoricoxib.
The present invention provides a stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Fig. 1: PXRD pattern of crystalline etoricoxib, which is substantially in accordance with
example 1.
Fig. 2 PXRD pattern of etoricoxib hemihydrate, which is substantially in accordance with
reference example 1.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for the preparation of crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta comprising:
a) treating etoricoxib with a solvent system comprising at least one solvent selected from the group consisting of glycols, polyalkylene glycols and mixtures thereof; and
b) isolating crystalline etoricoxib.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5, 18.1, 20.1, 22.7, 24.1 and 29.2 ±0.2 degrees 2 theta comprising :
a) treating etoricoxib with a solvent system comprising at least one solvent selected from the group consisting of glycols, polyalkylene glycols and mixtures thereof; and
b) isolating crystalline etoricoxib.
As used herein, "glycol" refers to an organic compound in which two hydroxyl groups are attached to different carbon atoms and includes ethylene glycol, propylene glycol, butylene glycol.
As used herein, "polyalkylene glycol" includes compounds such as polyethylene glycol (PEG), polypropylene glycol, polybutylene glycol and the like. Preferably, the polyalkylene glycol may be PEG having molecular weight range 200, 400, 800, 900, 1000, 1200, 2000 and 4000. More preferably the PEG may be PEG-400.
As used herein, "treating" refers to contacting, heating, crystallizing, slurrying, etoricoxib in a solvent system comprising at least one solvent selected from the group consisting of glycols and polyalkylene glycols.
In one embodiment, the solvent system comprises alcohols, nitriles, ketones, esters and at least one of glycols, polyalkylene glycols and mixtures thereof.

The alcohol may be selected from C1-C5 alcoholic solvent group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, tertiary butyl alcohol, isobutyl alcohol and the like. Preferably the alcohol may be isopropyl alcohol or its mixture with other alcohols.
Ketones may be selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone and the like.
Esters may be selected from the group consisting of isopropyl acetate, ethyl acetate, butyl acetate and the like.
Nitriles may be selected from the group consisting of acetonitrile, propionitrile, butyronitrile and the like.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, said process comprising treating etoricoxib with a solvent system comprising a C1-C5 alcohol and at least one solvent selected from the group consisting of glycols and polyalkylene glycols and isolating crystalline etoricoxib.
In one embodiment the solvent system comprises C1-C5 alcoholic solvent and polyalkylene glycol in the ratio of about 0.25: 550 by volume to about by 2.5:170 by volume. Preferably the ratio of C1-C5 alcoholic solvent and polyalkylene glycol is 0.5:450 by volume.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, the process comprising treating etoricoxib with a solvent system comprising C1-C5 alcohol and polyethylene glycol and isolating crystalline etoricoxib.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, the process comprising crystallizing etoricoxib from a solvent system comprising isopropyl alcohol and PEG-400 and isolating crystalline etoricoxib.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib, as described herein above, the process comprising crystallizing etoricoxib by heating a mixture of etoricoxib, a C1-C5 alcohol and PEG-400 to a temperature of about 60-80°C, preferably 70-75°C; cooling and isolating crystalline etoricoxib by techniques

known in the art. These isolation techniques include for example filtration, centrifugation, evaporation and the like.
In one embodiment, the present invention provides a process for preparation of stable crystalline etoricoxib, the process comprising heating a mixture of isopropyl alcohol, etoricoxib and PEG-400 to a temperature of about 60-85°C. Preferably, the mixture is heated to a temperature of about 70-75°C; stirring the resultant hot mixture until a clear solution is obtained; optionally, treating the hot solution containing etoricoxib with charcoal and filtering through hyflo; gradually cooling the hot solution . The cooling is preferably carried out under nitrogen atmosphere. The reaction mass is maintained at a temperature of about -5 to about 10 °C. Preferably, the reaction mass is maintained at a temperature of about 0-5°C. Crystalline etoricoxib thus formed is isolated by filtration. The wet cake of crystalline etoricoxib is dried under vacuum in a rotary cone vacuum drier for a period of about 15 to 33 hours. Preferably etoricoxib is dried under vacuum in a rotary vacuum drier for a period of about 18 to 23 hours. The dried etoricoxib is subjected to milling and sifting and packed in polyethylene bags and silica gel pouches are kept in between white and black polyethylene bags. This is further sealed with a polyvinyl chloride (PVC) strip and placed in triple laminated aluminium bags and the aluminium bags are sealed.
In one embodiment, the present invention provides a process for preparing crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5, 18.1, 20.1,22.7, 24.1 and 29.2 ±0.2 degrees 2 theta, the process comprising :
a) crystallizing etoricoxib with a solvent system comprising a C1-C5 alcoholic solvent and polyalkylene glycol; and
b) isolating crystalline etoricoxib.
The C1-C5 alcoholic solvent and polyalkylene glycol may be selected from the group as
disclosed earlier.
The polymorphic form IV, form V and hemihydrate form of etoricoxib are known in the art. Illustratively, form IV and hemihydrate are disclosed in EP1248618B1 (EP'618) and form V is disclosed in EP129695IB 1 (EP'951) and are included by reference herein in its entirety. Polymorphic form IV and form V are characterized by XRD peaks in EP'618 and EP'915 respectively. The XRD pattern of hemihydrate is disclosed in Fig. 5 of EP'618.

In one embodiment, etoricoxib hemihydrate was prepared by a process comprising addition of water to a solution of etoricoxib in acetone. The product was isolated and dried to obtain etoricoxib hemihydrate. The etoricoxib hemihydrate thus obtained is characterized by peak reflection at about 8.1±0.2 degrees 2 theta and an XRD pattern which is substantially in accordance with Fig. 2 and matches with that reported in Fig. 5 of EP'618.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the crystalline form of etoricoxib has no detectable quantity of form IV as determined by absence of characteristic peak reflections at about 8.7±0,2 degrees 2 theta.
In one embodiment, the present invention provides a process for the preparation of crystalline etoricoxib having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of form IV as determined by absence of characteristic peak reflections at about 8.7 and 15.2±0.2 degrees 2 theta.
In one embodiment, the present invention provides process for the preparation of crystalline etoricoxib having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of form V as determined by absence of characteristic peak reflections at about 13.7 ±0.2 degrees 2 theta.
In one embodiment, the present invention provides process for the preparation of crystalline etoricoxib having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of form V as determined by absence of characteristic peak reflections at about 6.5 and 17.7±0.2 degrees 2 theta.
In one embodiment, the present invention provides process for the preparation of crystalline etoricoxib having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta. wherein the stable crystalline form of etoricoxib has no detectable quantity of hemihydrate form as determined by absence of characteristic peak reflections at about 8.1 ±0.2 degrees 2 theta.

In one embodiment, the present invention provides a stable crystalline form of etoricoxib characterized by PXRD pattern, which is substantially in accordance with FIG 1.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD pattern with peaks at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD pattern with peaks at about 7.1, 9.7, 11.8, 18.8, 15.5,20.1,22.7,24.1 and 29.2 ±0.2 degrees 2 theta.
As used herein, the term "stable" refers to crystalline etoricoxib, characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 & 22.7 ±0.2 degrees 2 theta, which retains its original polymorphic form without undergoing polymorphic conversion over time.
In one embodiment, the present invention provides stable crystalline etoricoxib obtained by the process as described herein above having characteristic PXRD peak reflections at about 7.1. 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta and has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage.
In one embodiment, the present invention provides stable crystalline etoricoxib obtained by the process as disclosed above having characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta and has no detectable quantity of any of form IV, form
V or hemihydrate form of etoricoxib on storage.
The present invention provides a stable crystalline form of etoricoxib characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form
V or hemihydrate form of etoricoxib at room temperature or under accelerated stability
conditions for extended periods of time.
The present invention provides a stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form
V or hemihydrate form of etoricoxib on storage at about 25°C for a period of about two years.
In one embodiment, present invention provides stable crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7

±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage at about 2-8°C.
In one embodiment, present invention provides stable crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage at about 25°C and about 60% relative humidity (RH) for at least 2 months.
In one embodiment, present invention provides stable crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage at about 30°C and about 65%RH for at least 2 months.
The present invention provides a stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage at about 40°C and about 75% relative humidity for a period of about six months.
The term "no detectable quantity" refers to an amount of less than about 0.5% w/w. Preferably, less than about 0.1% w/w, still more preferably, absent.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, having no or little tendency to convert to any of the other polymorphic forms or solvates including hydrates.
In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of form II, contains less than about 1 % w/w of form II. Preferably, the stable crystalline etoricoxib of the present invention has no detectable quantity of form II.
In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of form III, contains less than about 1% w/w of form III. Preferably, the stable crystalline etoricoxib of the present invention has no detectable quantity of form III.

In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of form IV, contains less than about 1 w/w % of form IV. Preferably, the stable crystalline etoricoxib of the present invention has no detectable quantity of form IV.
In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of form V, contains less than about 1 % w/w of form V. Preferably, the stable crystalline etoricoxib of the present invention has no detectable form V.
In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of hemihydrate form, contains less than about 1 % of hemihydrate form. Preferably, the stable crystalline etoricoxib of the present invention has no detectable quantity of hemihydrate form.
In one embodiment, the stable crystalline form of etoricoxib of the present invention contains less than about 2% w/w of any of form II, form III, form IV, form V or hemihydrate form, contains less than about 1% w/w of any of form II, form III, form IV, form V or hemihydrate form. Preferably, the stable crystalline form of etoricoxib of the present invention has no detectable quantity of any of form II, form III, form IV, form V or hemihydrate form.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta wherein, the stable crystalline form of etoricoxib has no detectable quantity of form IV as determined by absence of characteristic peak reflections at about 8.7 ±0.2 degrees 2 theta.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta wherein, the stable crystalline form of etoricoxib has no detectable quantity of form IV as determined by absence of characteristic peak reflections at about 8.7 and 15.2 ±0.2 degrees 2 theta.
In one embodiment, the present invention provides stable crystalline form of etoricoxib. characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta wherein, the stable crystalline form of etoricoxib has no detectable quantity of form IV as determined by absence of characteristic peak reflections at about 13.7 ±0.2 degrees 2 theta.

In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta wherein, the stable crystalline form of etoricoxib has no detectable quantity of form V as determined by absence of characteristic peak reflections at about 6.5 and 17.7±0.2 degrees 2 theta.
In one embodiment, the present invention provides stable crystalline form of etoricoxib characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta wherein, the stable crystalline form of etoricoxib has no detectable quantity of hemihydrate form as determined by absence of characteristic peak reflections at about 8.1 ±0.2 degrees 2 theta. Instrumental settings for XRPD of stable crystalline etoricoxib:
The measurements were performed on Philips X-Ray Diffractometer model XPERT-PRO (PANalytical) Detector: X'celerator [1] using Cu lamp with type and wavelength of the X-ray radiation: K-Alphal [A] and 1.54060 under the following conditions: Generator settings: 40mA/45kV, Time per step: 50, Step size: 0.0167, Peak width 2.00 and start angle (°) 2.0 and End angle: 50.0, Scan type: continuous; measurement performed at 25°C. The XRPD instrument is calibrated using NIST SRM 6-40C silicon standard and NIST SRM 1976 Alumina.
Sample preparation: Adequate amount of sample was taken and filled in the sample holder using back-loading technique. Then sample holder was loaded between X-ray optics-path and scan using the above mentioned instrumental parameters. Integrated the obtained powder X-ray diffraction profiles using X' pert high score software.
Etoricoxib of a defined particle size may be produced by recrystallization from various solvents. It is well accepted that particle size plays an important role in the solubility properties of an active pharmaceutical ingredient (API). Particle size reduction leads to increase in surface area of the solid phase that is in contact with the liquid phase, thus leading to increased solubility. Rate of dissolution of a poorly soluble drug may limit its rate of absorption, thus affecting its bioavailability. In such cases, particle size reduction may enhance the absorption thus improving the bioavailability. Further, particle size can also affect how freely crystals or a powdered form of a drug will flow past each other, which in turn, has consequences in the production process of pharmaceutical products containing the drug. In view of all these it is desirable to have a defined particle size for an API.

The various techniques employed to attain a defined particle size are well known in the art. These methods include pH adjustment, cooling, evaporation of solvent, addition of antisolvent to a solution or by co-precipitation to obtain a precipitate with a defined particle size. Particle size of etoricoxib may be further adjusted by employing known methods of particle size reduction like compaction, milling or micronizing and sorting the milled product according to particle size.
In one embodiment of the present invention provides a process for preparing etoricoxib having D90 between 40-80 u.. The process involves feeding etoricoxb into a compactor wherein the hydraulic pressure is about 0.5 to about 0.8 ton. The compactor is set an RPM (rate per minute) of 3. Etoricoxib thus obtained are milled and finally sieved to get etoricoxib of the desired particle size.
In one embodiment of the present invention, the etoricoxib has D10 of about 2.91, D50 of about 15.68 and D90of about 55.9µ..
Particle size of etoricoxib was measured by Malvern Mastersizer 2000®.
In one embodiment the present invention relates to a pharmaceutical composition comprising a therapeutically effective amount of a storage stable crystalline etoricoxib.
The following examples are provided to enable one skilled in the art to practice the . invention and are merely illustrative of the invention. The examples should not be read as limiting the scope of the invention as defined in the feature and advantages.

EXAMPLES
COMPARATIVE EXAMPLE 1
Preparation of 5-chloro-3-[4-methylsulfonyI)phenyl]-2-(2-methyl-5-pyridinyl) pyridine,
etoricoxib.
In a 250ml 4-neck round bottom flask equipped with overhead stirrer, double surface condenser, thermowell pocket placed in water bath, 135ml (3volume) of isopropyl alcohol was added followed by 45.0gm etoricoxib; then the reaction mass was heated to about 65°C to about 70°C. The reaction mass was charcoalised with NORIT® charcoal and hot Filtered on a hyflo bed and washed with 45 ml (1 volume) hot isopropyl alcohol. The filtered mass was gradually cooled to about 25°C to about 30°C with continuous stirring and then further cooled to about 0°C to about 5°C and maintained for about an hour and then filtered and washed with 45ml (1 volume) isopropyl alcohol. The wet solids were dried in air oven. 38gm of etoricoxib was obtained. Reference Example 1: preparation of etoricoxib hemihydrate.
In a one litre 4-neck round bottom flask equipped with one condenser, dropping funnel, placed in a plastic bath was charged 25 gm etoricoxib and 125ml acetone. To this solution 250 ml water was added and the reaction mixture was stirred for about 2 hr at a temperature of about 25-30°C. the solid was filtered and dried to obtain etoricoxib hemihydrate.
Table 1: Below table provides XRD of etoricoxib hemihydrate.

Pos. [°2Th.] d-spacing
rAi Rel.
Int. [%] Pos.
[°2Th.] d-spacing
[A] Rel.
Int.[%] Pos. [°2Th.] d-spacing [A] Rel.
Int. [%]
8.1 10.8 22.7 19.6 4.5 16.6 25.9 3.4 8.6
8.3 10.5 15.3 19.9 4.4 12.0 26.3 3.3 6.1
12.8 6.86 1.6 20.0 4.40 12.9 27.7 3.2 17.0
13.7 6.4 1.9 21.3 4.1 100.0 27.9 3.1 7.3
13.9 6.3 3.0 21.9 4.0 9.4 28.0 3.1 4.7
14.4 6.1 20.0 22.2 3.9 10.5 28.9 3.0 14.4
15.4 5.7 26.2 22.4 3.9 18.9 29.8 2.9 3.2
15.9 5.5 34.1 22.9 3.8 2.4 30.5 2.9 2.9
16.2 5.4 8.1 23.4 3.7 58.7 30.7 2.9 4.1
16.8 5.2 96.1 23.6 3.7 22.9 31.1 2.8 6.3
17.5 5.02 11.0 24.5 3.6 52.0 31.6 2.8 8.5
19.5 4.5 33.4 25.5 3.4 32.1

EXAMPLE 1
Preparation of 5-chloro-3-[4-methylsulfonyl)phenyl]-2-(2-methyI-5-pyridinyl) pyridine,
etoricoxib
56 gm of etoricoxib, 448 ml of isopropyl alcohol and 0.56 gm of PEG-400 were charged into a
o
round bottom flask with stirring at about 25-30 C for about 5 minutes. The reaction mass was then heated to about 70-75 C and charcoal was added. The reaction mass was heated to a temperature of about 80-85 C. Stirring was continued for about 30 minutes to about 2 hours. Reaction mass was filtered through hyflo. The filtrate was stirred and cooled to about 0-15 C for about 1 hour. The reaction mass, was filtered and washed with isopropyl alcohol and dried the solid crystalline etoricoxib at about 80-85°C. Yield: 48 gm ; HPLC purity = 99.95%.
Table 2: Below table provides XRD of crystalline etoricoxib.

Pos[ 2th] Rel Int [%] Pos[ 2th] Rel Int [%] Pos[2th] Rel Int [%] Pos[ 2th] Rel Int [%]
7.1 29.5 19.3 8.2 23.6 10.8 31.2 4.0
9.7 18 20.1 10.4 23.9 10.8 31.6 0.6
11.8 26.3 20.2 3.2 24.1 20.5 31.9 0.7
12.4 11.6 21.1 8.0 25.0 2.02 33.1 0.8
13.0 2.2 21.2 8.8 26.3 7.24 33.5 0.5
14.1 0.4 21.4 4.9 26.8 1.28 34.7 2.6
15.5 29.7 21.8 10.0 27.6 2.25 35.7 2.5
16.6 100 22.5 8.5 28.3 1.77 39.2 3.5
18.1 98.1 22.7 22.9 29.2 11.6 40.0 0.9
18.8 1.2 22.9 6.3 29.8 3.67 40.6 0.4
19.1 4.8 23.2 12.6 30.7 2.57
The X-ray diffraction pattern was obtained using an X-ray diffractometer (Philips X'pert pro,
PANalytical). The crystalline etoricoxib as prepared above was filled into a sample holder using
back-loading technique. The sample holder was loaded between the X-ray optics path and
scanned.
Stability Data
Crystalline etoricoxib was stored at 40°C and 75% relative humidity. The content of other
polymorphic forms was measured at periodic intervals.
Table 3: Stability data of crystalline etoricoxib prepared by the present invention at periodic
intervals.

Time of
storage in months 15 days 1 month 2 month 6 months
Polymorphic form form IV form V hemi-hydrate form IV form
V hemi-hydrate form IV form
V hemi-hydrate form IV form V hemi-hydrate

Crystalline etoricoxib obtained from 0.42 NA 0.81 0.52 NA 0.9 1.43 NA 1.11 NA NA NA
comparative example 1
Stable crystalline etoricoxib obtained
from ND ND ND ND ND ND ND ND ND ND ND ND
example J
Table 1
*NA= Not applicable; ND = not detected
The results indicate that the crystalline form of etoricoxib of the present invention is stable and does not undergo polymorphic conversion at 40°C and 75% relative humidity. In contrast, the samples prepared according to comparative example 1 resulted to a substantial increase in the presence of other polymorphic forms at the end of two months under similar conditions.
Table 4: The table below provides percentage contamination with other polymorphic
form of crystalline etoricoxib obtained from comparative example 1.

Condition of storage Time

15 days 1 month 2 month
2-8°C Not detected 0.53 hemihydrate 0.58 hemihydrate
25°C at 60%RH 0.52 hemihydrate 0.55 hemihydrate 0.65 hemihydrate
30°C at 65% RH 0.66 hemihydrate 0.68 hemihydrate 0.69 hemihydrate and 1.23 form IV
Table 2
The above results indicate that etoricoxib prepared according to the present invention is chemically and physically stable at room temperature and accelerated stability conditions.

Claims:
1 .A process for the preparation of crystalline etoricoxib, characterized by PXRD pattern having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta comprising:
. a) treating etoricoxib with a solvent system comprising at least one solvent selected from the group consisting of glycols, polyalkylene glycols and mixtures thereof; and b) isolating the crystalline etoricoxib.
2. The process as claimed in claim 1, wherein the polyalkylene glycols have a molecular weight of 200,400, 800, 900, 1000, 1200,2000 and 4000.
. 3. The process as claimed in claim 2, wherein the polyalkylene glycol is polyethylene glycol.
4. The process as claimed in claim 3, wherein the polyethylene glycol is PEG-400.
5. The process as claimed in claim 1, wherein the solvent system comprises C1-C5 alcoholic solvent is selected from the group consisting of methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, tertiary-butanol and mixtures thereof.
6. The process as claimed in claim 1, wherein the solvent system comprises C1-C5 alcoholic solvent and polyalkylene glycol in the ratio of about 0.25:550 by volume to about 2.5: 170 by volume.
7. The process as claimed in claim 1, wherein the treatment comprises crystallizing etoricoxib from a solvent system comprising C1-C5 alcoholic solvent and polyalkylene glycol.
8. The process as claimed in claim 1, wherein the crystalline etoricoxib obtained has characteristic PXRD peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta and has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage.

9. A stable crystalline form of etoricoxib characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage.
10. The stable crystalline form of etoricoxib as claimed in claim 9, characterized by PXRD having peak reflections at about 7.1, 9.7, 11.8, 15.5 and 22.7 ±0.2 degrees 2 theta, wherein the stable crystalline form of etoricoxib has no detectable quantity of any of form IV, form V or hemihydrate form of etoricoxib on storage at about 40°C and about 75% relative humidity for a period of about six months.